Washing composition



Patented Oct. 28, 1952 2,615,846- WASHING COMPOSITION Vladimir Dvorkovitz, Winnetka, Englewood, N. J--.,. assignors'to.

The Diversey Corporation,

G.. Hawley, Jr.,

Illinois 111., and Thomas a corporation of No Drawing. Application December 1, 1951,

Serial No. 259,485;

10 Claims.

This invention relates to methods of treating hard water to. produce a washing solution, washing solutions, and methods of washing surfaces such as the surfaces of articles.

This application is a continuationin-part of our application Serial No. 777,112 filed September 30, 1947, now Patent No. 2,584,017, issued January 29, 1952.

The industries that wash large quantities of bottles and other glassware, metal surfaces, china, porcelain, enamelware, rubber, synthetic rubber, and similar surfaces necessarily make up their cleaning solutions with water that is more or less hard and employ a strongly alkaline solution such as that produced'with a. caustic alkali in order to secure complete cleansing and, particularly in the food industry, complete or-partial disinfection.

Such strongly alkaline solutions have been found particularly useful in washing bottles and other glassware such as that used in the dairy, brewery. and soft drink industries. Here,- asv in similar industries, the users have found it.expedient to adopt a continuous process wherein the bottles or other articlesare conveyed first through a tank or tanks containing a strongly alkaline. solution and then through a rinsing solution. When the articles pass through the alkaline solution, they are coated with a. film of alkali. When the thusly coated objects are immersedin. rinse. water, an immediatev precipitatiorroccurs of the dissolved calcium and magnesinmsalts that are present. in the. rinse water. Further precipitated solids are also formed inthe wash water by the addition of the caustic alkali. to. the wash water. These precipitated solids interfere withv the proper operation of the. washmg. equipment, deposit unsightly films on the articlesbeing washed, and because of the intimate contact of the alkaline film on theiarticles, and: equipment before contacting the wash water. often deposits a hard adherent and rock-like scale. Thus, in every'step of the washing operation from the first formation of the washing solution to the final rinsing operation, the precipitated calcium and magnesium salts interfere and prevent efficient washing.

The problem of preventing this precipitation ofthehardness constituents by the caustic alkali andthe removal of scale formed has received considerable recognition and much effort has been spent to prevent or overcome it. For example, many complex phoric acid have the property of holding normally insoluble calcium and magnesium compounds in solution. Certain amino carboxylic acid derivatives have also been used for this purpose. It has been found, however, that none of these compounds works effectively in the presence of sodium hydroxide. Thus, a sufficient quantity of sodium hexametaphosphate will hold the hard water precipitates usually obtained by adding sodium carbonate or sodium orthophosalkali metal salts of phosphate. toa hard .water, solution. Howevenlong standing of the. product. or standing at lesstime at elevated temperatures causes hydrolysis of the. resulting complexand' causes precipitation of the calciumand magnesium com-pounds. This effect is even.more pronounced if even small quantities ofcaustic alkalis are present.

Theipresent invention is concerned with means" for preventing the formation of this hardness constituent, preventing or materially reducing the precipitation. of the hardness constituents from the hard water and reducing the dissolving,

action ofthe. caustic'alkali on glasswarachina, porcelainand similar articles: We have found F that a composition comprising a caustic alkali such as an alkali metalhydroxideancl particularly sodium" hydroxide. or potassium. hydroxide and an alkali metal gluconate and particularly. sodium gluconate or potassium gluconate will prevent or-at, least minimize the formation of the scale, the-precipitation of the hardness constituents from hard water and the attack of the caustic alkali onthe glassand-similar surfaces.

The hydroxides and gluconates of sodium and potassium are preferred because'of' their inexpensiveness and'availability but the hydroxides of'other elements'of the alkali metal group may beused if desired.

The fact that these salts will not form precipitates in the presence of sodium hydroxide is surprising as ithas been noted that precipitates. will form when such alkalis as, sodium carbonate,

sodiumorthophosphate, sodium silicate and the. like are; employed with the salts in the. absence.

of sodium l'nrdroxide and the like.v Thesev alkaline. materials maybe. used,..however, if' they are. used in combination withv the sodium hydroxide. or other caustic alkali...

It has. been foundth'at everrif some precipitation: is. formedzo-n the washing? equipment or is mechanically picked up by theuequipment in its. passage through theirinse: water, it is. redissolved. when itzis; repassed through the caustic alkaligluconate solution.

The solution is quitestableand can be maintained at F. or above'for two weeksor more without any-apparent decomposition or precipi-- tation. The solution isparticularly useful in those washing'operations' where an closedv systemis employed either: in a' batch washing such as:

mechanical dish washers, a continuous: recirculation such. as washing the passagesof pasteurizers, the; circulation ofthe articles through the wash and: rinse water such. as'occurs in industrial bottle. and othergl'assware washing orwashingyof .a similar nature... Where the. washing solution is: freshly made up, used and thenimmediately, discarded, the problems of precipitation of the hardness constituents .and scale formation are much minimized; However, ittisapparent that even here thecompositionsand solutions. of this invention are beneficial in that precipitation in the washing solution itself is prevented or materially reduced.

The washing solution of this invention comprises essentially about 0.25-20% caustic alkali, 0.025-2.0% alkali metal gluconate and at least about 78% water, with all percentages being by weight. Thus, hard water may be treated to produce a washing solution by adding these amounts of caustic alkali and gluconate to the hard water.

The caustic alkali may be any alkali metal hydroxide and preferably either sodium or potassium hydroxide. Similarly, the gluconate may be any alkali metal gluconate and particularly the sodium or potassium compound. The washing solution should be substantially free from ions capable of precipitating substantial amounts of calcium and magnesium salts in the presence of alkali metal gluconate so that the solution will be relatively free from precipitates. Ordinarily such compounds as the soluble silicates and phosphates do cause precipitation of substantial amounts of the calcium and magnesium salts in the presence of the gluconate.

The washing solutions of this invention have been found eifective in washing surfaces, and particularly articles of glass, metal, china, porcelain, enamel, natural rubber, synthetic rubber, and the like. Thus, these solutions have been used for washing bottles and other glassware, for circulating through the metal parts of pasteurizing equipment, for washing milk condensing pans and milk condensing equipment, for washing china dishware and other china articles, for washing porcelainware and enamelware, and for washing various rubber articles and surfaces such as the rubber infiations used in vacuum milker systems.

At the lower portions of the 0.25-20% caustic alkali and the 0.025-2% alkali metal gluconate ranges, there may be some precipitation of insoluble matter particularly where the water used is extremely hard. However, this relatively small precipitation is not harmful as it is ordinarily non-adherent. Furthermore, those skilled in the art understand that higher proportions are employed where necessary to control precipitation of the hardness constituents from extremely hard water. Similarly, higher amounts of caustic alkali within the ranges are preferably avoided when washing glass, china, porcelain and the like because of the softening effect of the higher concentrations of alkali. However, the choic of amounts within the range to minimize this softening effect is well understood by those skilled in the art. As is customary when i selecting amounts of two or more ingredients over a relatively wide range, the amount of gluconate in the lower portion of the range is used when an amount of caustic is employed within the lower portion of its range. Similarly, when the amount of caustic is within the upper part of its range, the amount of gluconate is also in the upper portion of its range. Ordinarily, amounts within the upper portions of the ranges are used when the surface or article washed is to be completely sterilized and the material such as metal, rubber and the like, is resistant to the relatively high amounts of caustic alkali. Where the material being washed such as glass is susceptible to attack by the alkali even with the gluconate present, the upper limit of the caustic should not be above 10% and the gluconate 1% and these upper limits in the case of glass and NQOH, KOH, Na. om- K. Glu- Percent Percent $5 33}; $3333,

Solution Slight prec. Clear Slight prec. Clear Clear Clear Clear Clear Clear Clear Clear gllezilr ig tprec. Clear Slight prec. Slight prec. Clear Slight prec. Clear Clear Clear Clear Clear Clear Clear Clear 5 Clear 0 Slight prec. 0 Clear 0 Slight prec.

The solution of this invention has a pH of more than 12 for most eifective results. The caustic alkali and gluconate combination materially reduces the softening and subsequent scratching of glass. It has been found that the addition of such agents as trisodium phosphate, sodium carbonate, or the like, to caustic alkali solutions assist in the cleaning of glassware. However. these agents have a marked effect in that they serve as catalysts for the sodium hydroxide and cause it to soften and partially dissolve the glass. This is also true with similar articles such as china, porcelain and the like. Thus, these materials are more easily marked by the machinery used in the wash or by abrasion against other pieces. The use of the caustic alkali and gluconate solutions successfully; avoids this undue softening and dissolving. 'Various tests have been made to prove these facts; Thus a series of solutions was prepared using 5% concentrations of sodium hydroxide. The materials used and the results obtained are shown in the following table. In obtaining these results, the glass was held in contact with each solution for 72 hours at 145 F.

TABLE II M Percent loss Y g gj z fgi in weight of Composition 01 milk dgreinbsoit rin ottlc bottle glass K185 s x 7 NaOH 107; Sodium gluconate NuOH 102 .092 95.0% NaOH- gf g lg g g A1 .077 .067

i. a 7 4 m naiuorl J57 94.7% Ni0H 5.0 So ium g neonate .054 .5%Nullapon B 052 94.0% NaOH 4.0% Trisodium phosphate 117 2.0% Sodium aluminate. 75

Another advantage to be obtained by the use of the caustic alkali and gluconate combination is that the solution serves as a better inhibitor of rust and corrosion of steel and iron than caustic alkali alone. Still another advantage is that the solutions are relatively non-foaming.

The solutions may include alkali stable wettin agents such as the alkali salts of higher alkyl sulfates, sodium dodecyl benzene sulfonate, alkyl naphthalene sodium sulionates, sodium salts of sulfonated ethers, as well as many others.

The solutions of this invention are particularly useful for washing and cleaning food handling equipment and containers although other types of equipment, articles and containers can also be cleaned efficiently as explained above. In the food handling industries and particularly for washing glassware and the like, a useful range of concentration for the washing solutions has been found to be about 3-5% caustic alkali, and 03-05% alkali metal gluconate.

The gluconates are known to give the corresponding lactones when subjected to an intermolecular dehydration process. In an aqueous solution of a caustic alkali, the lactone hydrolizes to give the alkali metal gluconate. Thus, it is possible to use the corresponding lactone in place of the gluconate and the description and the claims herein are intended to include the use of such a lactone that is hydrolized in solution to the salt. Similarly, a gluconic acid instead of the alkali metal gluconate can be used and is intended to be included in this invention as the gluconic acid will immediately react with some of the caustic alkali to form the alkali metal gluconate.

The foregoing detailed description is given for clearness of understanding only, and no unnecessary limitations should be understood therefrom, for some modifications will be obvious to those skilled in the art.

We claim:

1. In the washing of glassware, metal, rubber and the like with water containing dissolved calcium and magnesium salts with highly caustic solutions, the method of preventing deposit of unslightly films on the articles being washed which comprises adding to the hard water about 0.25-20% by weight of caustic alkali and about 0.025-2% by weight of alkali metal gluconate, the additions being free from ions capable of precipitating substantial amounts of calcium and magnesium salts in the presence of alkali metal gluconate whereby the alkali metal gluconate substantially inhibits precipitation of the calcium and magnesium salts of the hard water.

2. The method as set forth in claim 1 in which the solution contains at least about 78% water.

3. The method of claim 1 wherein the caustic alkali is employed in an amount of about 0.25-5.0% and the gluconate in an amount of about 0.025-0.5%.

4. The method of claim 1 wherein the caustic alkali is caustic soda and the gluconate is sodium gluconate.

5. A washing solution consisting essentially of about 0.2520% by weight of caustic alkali, about 0.0252.0% of alkali metal gluconate, and at least about 7 8% of water, the solution being substantially free from ions capable of precipitating substantial amounts of calcium and magnesium salts in the presence of alkali metal gluconate.

6. The solution of claim 5 wherein the caustic alkali is present in an amount of about 0.25-5.0% and the gluconate in an amount of about 0.025-0.5%.

7. The solution of claim 6 wherein the caustic alkali is caustic soda and the gluconate is sodium gluconate.

8. The method of treating hard water to produce a washing solution comprising adding to the hard water about 35% by weight of caustic alkali and about 03-05% of alkali metal gluconate.

9. A washing solution consisting essentially of about 35% by weight of caustic alkali, about 03-05% of alkali metal gluconate and water.

10. The method of washing articles which comprises applying thereto a solution consisting essentially of about 35% by weight of caustic alkali, about 03-05% of alkali metal gluconate and Water.

VLADIMIR DVORKOVITZ. THOMAS G. HAWLEY, JR.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 729,600 Jones June 2, 1902 2,145,827 Chester Jan. 31, 1939 2,291,085 Lehmkuhl et a1. July 28, 1942 2,346,562 De Long Apr. 11, 1944 2,419,805 Wegst et al Apr. 29, 1947 FOREIGN PATENTS Number Country Date 885,521 France May 31, 1943 

1. IN THE WASHING OF GLASSWARE, METAL, RUBBER AND THE LIKE WITH WATER CONTAINING DISSOLVED CALCIUM AND MAGNESIUM SALTS WITH HIGHLY CAUSTIC SOLUTIONS, THE METHOD OF PREVENTING DEPOSIT OF UNSLIGHTLY FILMS ON THE ARTICLES BEING WASHED WHICH COMPRISES ADDING TO THE HARD WATER ABOUT 0.25-20% BY WEIGHT OF CAUSTIC ALKALI AND ABOUT 0.25-2% BY WEIGHT OF ALKALI METAL GLUCONATE, THE ADDITIONS BEING FREE FROM IONS CAPABLE OF PRECIPITATING SUBSTANTIAL AMOUNTS OF CALCIUM AND MAGNESIUM SALTS IN THE PRESENCE OF ALKALI METAL GLUCONATE WHEREBY THE ALKALI METAL GLUCONATE SUBSTANTIALLY INHIBITS PRECIPITATION OF THE CALCIUM AND MAGNESIUM SALTS OF THE HARD WATER. 